Polarization measurement device and method

Abstract

In one embodiment, a polarization measuring device comprises a light source, a reticle positioned below the light source, an opaque frame having a single aperture, the opaque frame positioned below the reticle, a lens positioned below the opaque frame, and a wafer having photoresist on its surface. The aperture of the frame allows no more than a first light ray to pass from the light source through the reticle and the lens onto a first surface point on the photoresist. The aperture of the frame also allows no more than a second light ray to pass from the light source through the reticle and the lens onto a second surface point on the photoresist. The degree of polarization of the light source can be determined from the first amount of light absorbed at the first surface point and the second amount of light absorbed at the second surface point.

What is claimed is:  
     
       1. A method for measuring the polarization effect on a photoresist during photolithography, said method comprising the steps of: 
       providing an opaque frame between a reticle and a lens, said opaque frame having a single aperture which allows no more than a first light ray to pass from a light source through said reticle and said lens onto a first surface point on said photoresist, said aperture allowing no more than a second light ray to pass from said light source through said reticle and said lens onto a second surface point on said photoresist, said second surface point different from said first surface point; and  
       comparing a first amount of light received on said first surface point with a second amount of light received on said second surface point.  
     
     
       2. The method of  claim 1 , wherein each of said first light ray and said second light ray has a corresponding single angle of incidence. 
     
     
       3. The method of  claim 1 , wherein said opaque frame comprises a base, said aperture defined in said base, said opaque frame further comprising sidewalls extending from said base, said sidewalls contacting a bottom surface of said reticle. 
     
     
       4. The method of  claim 1 , wherein said opaque frame comprises aluminum. 
     
     
       5. The method of  claim 1 , wherein said photoresist at said first point is exposed only to said first light ray and wherein said photoresist at said second point is exposed only to said second light ray. 
     
     
       6. The method of  claim 1 , wherein said light source is determined to be randomly polarized if said first amount of light is the same as said second amount of light. 
     
     
       7. The method of  claim 1 , wherein said light source is determined to be polarized if said first amount of light is different from said second amount of light. 
     
     
       8. A method for measuring the polarization effect on a photoresist during photolithography, said method comprising the steps of: 
       providing an opaque frame between a reticle and a lens, said opaque frame having a single aperture which allows no more than a single light ray to pass from a light source through said reticle and said lens onto a surface point on said photoresist; and  
       determining a amount of light absorbed on said surface point on said photoresist, wherein said degree of polarization of said light source is determined from said amount of light absorbed on said surface point.  
     
     
       9. The method of  claim 8 , wherein said single light ray has a single angle of incidence. 
     
     
       10. The method of  claim 8 , wherein said photoresist at said surface point is exposed only to said single light ray. 
     
     
       11. The method of  claim 8 , wherein said opaque frame comprises a base, said aperture defined in said base, said opaque frame further comprising sidewalls extending from said base, said sidewalls contacting a bottom surface of said reticle. 
     
     
       12. A polarization measuring device for measuring the polarization effect on a photoresist during photolithography, said polarization measuring device comprising: 
       a light source;  
       a reticle positioned below said light source;  
       an opaque frame having a single aperture, said opaque frame positioned below said reticle;  
       a lens positioned below said opaque frame; and  
       a wafer having said photoresist on a surface of said wafer, said wafer positioned below said lens, said aperture allowing no more than a first light ray to pass from said light source through said reticle and said lens onto a first surface point on said photoresist; wherein said aperture further allows no more than a second light ray to pass from said light source through said reticle and said lens onto a second surface point on said photoresist, said second surface point different from said first surface point, and wherein said photoresist at said first point absorbs a first amount of light, and said photoresist at said second point absorbs a second amount of light, wherein said light source is determined to be randomly polarized if said first amount of light is the same as said second amount of light.  
     
     
       13. The polarization measuring device of  claim 12 , wherein said light source is determined to be polarized if said first amount of light is different from said second amount of light.